1. Field of the Invention
The present invention relates to a servo motor encoder, and more particularly, to an improved technique of using signal lines and output terminals in common thereby reducing the number of signal lines.
2. Description of the Related Art
FIG. 1 illustrates the structure of a conventional servo motor encoder.
In FIG. 1, reference numeral 1 denotes an incremental signal generator for outputting 3-phase incremental signals A, B, and Z (phases A, B, and Z). The incremental signals A, B, and Z are input to corresponding first drivers 2A, 2B, and 2C. Each first driver 2A, 2B, and 2C is connected to a corresponding pair of output terminals 2Aa, 2Ba, and 2Ca so that output incremental signals A, A, B, B, Z, and Z having different phases are output via these output terminals 2Aa, 2Ba, and 2Ca.
Reference numeral 10 denotes a servo motor magnetic pole position detection signal generator for outputting 3-phase servo motor magnetic pole position signals UE, VE, and WE (phases UE, VE, and WE), which are input to corresponding second drivers 11A, 11B, and 11C. Each second driver 11A, 11B, and 11C is connected to a corresponding pair of output terminals 11Aa, 11Ba, and 11Ca so that output servo motor magnetic pole position detection signals UE, UE, VE, VE, WE, and WE having different phases are output via the corresponding output terminals 11Aa, 11Ba, and 11Ca.
The output incremental signals A, A, . . . , Z, Z described above are used for position detection, and the output servo motor magnetic pole position detection signals UE, UE, . . . , WE, WE are used to switch driving coils of a servo motor (not shown).
The above-described conventional servo motor encoder has problems as described below.
The output incremental signals and the output servo motor magnetic pole position signals are output via the output terminals which are provided for exclusive use by the corresponding signals, and thus a great number of signal lines, twelve lines in this specific example, are required for connections between the output terminals and the encoder. This leads to difficulty in connecting signal lines to the output terminals in an assembling process of an encoder. The great number of signal lines also lead to great complexity in a signal processing circuit at a receiving end.